Shido from High School of the Dead really freaked me out. He held a freakin' orgy with high school students...
Tucker from FMA. The way he talked was really creepy. And how he used his daughter in a genetic experiment.
Alucard from Hellsing scared the crap out of me when a first saw him.
Tomie from Tomie. She's really scary.....
Mitsuhide from Sengoku Basara. He was weird...

I know this is a little late of a reply but the character is Sakurazuka Seishiro who appears in both Tokyo Babylon and X/1999. Just like most CLAMP characters some alternate reality version of him also pops up in Tsubasa: Reservoir Chronicles.